Opinion | The Islamic State Is Like a Chronic Disease

Four years ago, a sympathizer of the Islamic State told me that the group’s caliphate was hardier than believed and would survive near-total loss of territorial control. “So long as there is one street in one village where the caliph carries out Islamic law,” he told me, “the dawla will be legitimate.” (“Dawla” means state in Arabic.) All Muslims would remain obliged to travel there, he said. (It would be one very crowded street.) No rival caliph could challenge Abu Bakr al-Baghdadi, the Islamic State’s leader, as long as he ruled this alley and did it according to Islam.

Last week, the caliphate finally dwindled down to that one alley, and on Saturday it vanished entirely.

The Syrian Democratic Forces sacked the Islamic State’s last minuscule barrio in the town of Baghuz, in eastern Syria, after a weekslong siege. “One street in one village” may overstate the size of that last patch. In recent video attributed to the Islamic State, apparently from just days ago, the area looked like a small junkyard defended by vagrants. Several years back, the Islamic State circulated videos of its fighters living among swimming pools and well-stocked shops. In the junkyard videos, it looked as if no one had bathed for weeks. Many of the inhabitants hobbled around on crutches, and some of the few working vehicles were wheelchairs.

To see the Islamic State reduced to these indignities is a pleasure worth savoring. Now that we’ve savored it, though, it is time to confront the threat that remains — which is not merely, as President Trump claimed this weekend, “losers” who will “resurface” “on occasion.” It is a systemic threat.